Earth and Planetary Science Letters最新文献

{"title":"Titanium isotopes as a tracer of eclogite in the mantle sources of continental intraplate basalts","authors":"Jian Zhao ,&nbsp;Xiao-Jun Wang ,&nbsp;Xin-Miao Zhao ,&nbsp;Jian-Qiang Liu ,&nbsp;Gang Zeng ,&nbsp;Chun-Xia Yi ,&nbsp;Bing Liu ,&nbsp;Jin Li ,&nbsp;Xiang-Kun Zhu ,&nbsp;Li-Hui Chen","doi":"10.1016/j.epsl.2025.119366","DOIUrl":"10.1016/j.epsl.2025.119366","url":null,"abstract":"<div><div>Recycled oceanic crust and sediments play a crucial role in generating the chemical and lithological heterogeneity of the Earth's mantle. However, unequivocally identifying the lithological properties of these recycled crustal materials in the mantle sources of basalts remains a challenge, despite its significant implications for mantle dynamics and the generation of magma diversity. Here, we explore titanium (Ti) stable isotopes as a novel method for tracing eclogite melting in the source of intraplate basalt. We present new Ti isotope data for a suite of well-characterized intraplate basalts from northeast (NE) China, which were thought to be formed through interaction between primitive low-MgO melts derived from eclogitic recycled crust and the local lithospheric mantle peridotite. Results show that these basalts display large Ti isotopic variation, with δ^49/47Ti values ranging from −0.05‰ to 0.14‰. The δ^49/47Ti values are well correlated with radiogenic Sr–Nd–Pb isotopes and stable Fe isotopes, suggesting the mixing of two endmembers with distinct Ti isotopic compositions. The low-δ^49/47Ti endmember exhibits depleted Sr–Nd isotopic compositions that resemble those of the local lithospheric mantle peridotite. The high-δ^49/47Ti endmember (δ^49/47Ti ≥ 0.14‰) is characterized by an elevated δ^57/54Fe value (≥ 0.3‰) and low values of MgO (≤ 5 wt.%), CaO/Al₂O₃ (≤ 0.4), Nb/Nb* (≤ 0.7), and Ti/Ti* (≤ 0.6), which require an eclogite melt component in equilibrium with residual rutile in the source. Our thermodynamic modeling and mass balance calculations further suggest that such a melt can be produced by partial melting of a rutile-bearing eclogite, which has a protolith of mixed recycled oceanic crust and sediments. Therefore, this study highlights that Ti isotopes can serve as a novel tool for identifying the contribution of rutile-bearing eclogite to intraplate basalts.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"660 ","pages":"Article 119366"},"PeriodicalIF":4.8,"publicationDate":"2025-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143843664","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Cerium isotopic fractionation during magmatic processes and the composition of the upper mantle","authors":"Fang Liu ,&nbsp;Hongli Zhu ,&nbsp;Michael R. Perfit ,&nbsp;Xin Li ,&nbsp;Yajun An ,&nbsp;Mingxing Ling ,&nbsp;Zhaofeng Zhang","doi":"10.1016/j.epsl.2025.119365","DOIUrl":"10.1016/j.epsl.2025.119365","url":null,"abstract":"<div><div>Cerium (Ce) is a refractory, incompatible and redox-sensitive element and its isotopes can be used to trace planetary accretion and evolution in the early solar system. A knowledge of the isotopic composition of rocks that sample from the Earth's mantle is a prerequisite to understand curst-mantle evolution. In this study, we present the first comprehensive high-precision Ce stable isotopic compositions of different types of igneous rocks, including sixteen normal mid-ocean ridge basalts (N-MORB) from the East Pacific Rise (EPR) and Juan de Fuca Ridge (JdF), two depleted mid-ocean ridge basalts (D-MORB) from the EPR and Ecuador Rift, seven evolved lavas (basaltic andesites, andesites, and dacites) from the EPR. These igneous rocks, spanning compositions from primitive basalt to evolved dacite with MgO contents decreasing from 8.09 to 0.80 wt. %, display a limited variation in δ¹⁴²Ce from -0.038 to 0.024 ‰. Although these rocks have experienced different amounts and proportions of olivine, clinopyroxene, plagioclase, Fe-Ti oxides, and apatite fractional crystallization, no Ce isotopic fractionation was detected. The δ¹⁴²Ce values of MORBs show no correlation with La/Sm_(N) or Nb/Y, indicating that partial melting process cannot induce significant Ce isotopic fractionation. Our batch non-modal melting modelling shows that more than 95 % of the Ce budget will be extracted into melt after only 5 % degree of partial melting. Therefore, we conclude that Ce isotopic fractionation during magmatic processes is insignificant and the average δ¹⁴²Ce of studied samples of -0.005 ± 0.028 ‰ (2SD, <em>N</em> = 25) can be the best estimate of upper mantle's isotopic composition. Based on simple mass-balance calulation, the Ce isotopic composition of the bulk silicate Earth (BSE) is roughly estimated to be -0.008 ± 0.025 ‰ (2SD, propagated error).</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"661 ","pages":"Article 119365"},"PeriodicalIF":4.8,"publicationDate":"2025-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143852231","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Water solubility in nominally anhydrous minerals in a silica-rich system at the top lower mantle","authors":"Luyao Chen ,&nbsp;Zhaodong Liu ,&nbsp;Xinyu Zhao ,&nbsp;Chaowen Xu ,&nbsp;Dongyang Ju ,&nbsp;Bingtao Feng ,&nbsp;Jinze He ,&nbsp;Ran Liu ,&nbsp;Xinyang Li ,&nbsp;Wei Du ,&nbsp;Bingbing Liu ,&nbsp;Wenliang Xu","doi":"10.1016/j.epsl.2025.119360","DOIUrl":"10.1016/j.epsl.2025.119360","url":null,"abstract":"<div><div>Although aluminous stishovite plays an important role in water transport and storage in the lower mantle, its water capacity in the top lower mantle is still poorly constrained. Here, we systematically investigated the water solubility in aluminous stishovite coexisting with bridgmanite, periclase, calcium ferrite-type phase, etc., in the presence of hydrous melts in a silica-rich MgO–Al₂O₃–SiO₂–H₂O system at pressures of 23–32 GPa and temperatures of 1600–2100 K using tungsten carbide anvils in a Walker-type large-volume press. Aluminous stishovite can accommodate significant amounts of water up to ∼3611 ppm wt., while the coexisting nominally anhydrous minerals have a very limited water storage capacity and are nearly dry. The water solubility in stishovite increases almost linearly from ∼296 to ∼3611 ppm wt. H₂O with increasing Al₂O₃ content from ∼0.3 to 3.0 wt. %. Our study further suggests that aluminous stishovite is a dominant phase for water transport and storage in a subducted oceanic crust at depths of 660–850 km, while the top peridotitic or pyrolitic lower mantle is nearly dry at least up to 850 km owing to the dry major phases of bridgmanite and periclase. The high water storage capacity of aluminous stishovite may prevent the occurrence of partial melting caused by the release of water from subducted slabs at the top of the lower mantle. The presence of hydrous aluminous stishovite may provide a plausible explanation for the high conductivity anomalies occasionally observed in some subducted slabs in the top lower mantle.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"660 ","pages":"Article 119360"},"PeriodicalIF":4.8,"publicationDate":"2025-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143834936","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Volcanic gases reflect magma stalling and launching depths","authors":"Shuo Ding ,&nbsp;Terry Plank ,&nbsp;J. Maarten de Moor ,&nbsp;Yves Moussallam ,&nbsp;Maryjo Brounce ,&nbsp;Peter Kelly","doi":"10.1016/j.epsl.2025.119349","DOIUrl":"10.1016/j.epsl.2025.119349","url":null,"abstract":"<div><div>Many open-vent arc volcanoes display two modes in their continuous gas emissions, one with a characteristic CO₂/ S_T ratio typical of periods of quiescent degassing and another punctuated by high CO₂/ S_T gas emitted in the weeks before eruption, a recently recognized eruption precursor. In this study we explore the origin of the two modes of degassing revealed by time-series gas data at Turrialba volcano (Costa Rica) in the context of new melt inclusion (MI) data. To reconstruct the c[CO₂] of undegassed magma, we developed a rapid-quench piston-cylinder assembly to rehomogenize the vapor bubble commonly contained in MIs. We focus on olivine-hosted MIs from a mafic scoria sample erupted from Turrialba in 1864–1866. The reconstructed CO₂ contents in MIs decrease from ∼4000 to &lt;1000 ppmw as S contents decrease from 3500 to &lt;1000 ppmw. The highest reconstructed S and CO₂ in the MIs resulted in an initial magmatic CO₂/ S_T ratio (molar) of 0.83. Informed by the MI data, we modeled the decompression degassing of Turrialba magma and vapor composition using the Sulfur_X and EVo models. Instead of being controlled by initial magmatic CO₂/S_T ratio as suggested by previous studies, we find that the quiescent gas emitted from Turrialba during 2014–2018 (CO₂/ S_T = 2.3 ± 0.8, molar) appears to reflectequilibrium with magmas stored at 4–8 km (Sulfur_X) or 2 km (EVo) depth, when H₂O is degassing extensively from the magma. A magma storage region at 4–8 km is also supported by seismic tomography. The second gas mode is noted by spikes in CO₂/ S_T ∼ 7.9 ± 2 in the weeks prior to eruption. This gas reflects equilibrium with a magma at 12–18 km (Sulfur_X) or 4–8 km (EVo), where the ascending magma is saturated with a CO₂-rich vapor. Thus, there are two important trans crustal depths beneath the volcano: one where the rate of H₂O loss from the magma and thus magma viscosity increases, and one at greater depths where high CO₂/S_T vapor forms and may facilitate dike propagation. We interpret the shallower, H₂O-loss region as the main site of magma stalling and storage, where quiescent gas is generated continuously. We interpret the greater depth (12–18 km) as the source of the precursory gas that precedes eruption, and where the mafic melt lastly equilibrated with a mush zone before ascending and triggering eruption weeks later. This hypothesis is ripe for testing at other volcanoes that exhibit two modes in gas geochemistry.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"660 ","pages":"Article 119349"},"PeriodicalIF":4.8,"publicationDate":"2025-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143834935","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Thor: a rock strength database for investigating lithologic controls in landscape evolution","authors":"Mauricio B. Haag ,&nbsp;Lindsay M. Schoenbohm","doi":"10.1016/j.epsl.2025.119364","DOIUrl":"10.1016/j.epsl.2025.119364","url":null,"abstract":"<div><div>Topographic information has been widely used to provide insights into tectonics and climate. However, these metrics are subject to lithologic effects that limit our understanding of how landscapes grow, evolve, and decay. To address this, we compile over 6100 Schmidt hammer-based rock strength measurements from 264 published studies to create an extensive rock strength database that we call <em>Thor</em>. We use this database to perform a meta-analysis that enables us to quantify, on a global scale, the impact of lithology on fluvial metrics. Our findings reveal a strong correlation between topographic metrics and rock strength, particularly the normalized steepness index (<em>k_sn</em>) and the fluvial erodibility coefficient (<em>K</em>). Additionally, using four case studies worldwide we identify that incorporating rock strength data improves the correlation between measured and predicted erosion rates for all sites, regardless of tectonic activity and climate setting. While we acknowledge the roles of climate and tectonics in shaping Earth's surface, our findings reveal a notable influence of lithology in landscape evolution, both globally and locally. These findings underscore the potential bias introduced by spatially variable lithology on commonly used topographic metrics for inferring drainage reorganization, incision, tectonics, and climate forcing.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"660 ","pages":"Article 119364"},"PeriodicalIF":4.8,"publicationDate":"2025-04-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143825921","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"CaCO3 precipitation kinetics and polymorphism in ferruginous seawater","authors":"Ben Davis Barnes ,&nbsp;Clancy Zhijian Jiang ,&nbsp;Peter Methley ,&nbsp;Justin V. Strauss ,&nbsp;Nicholas J. Tosca","doi":"10.1016/j.epsl.2025.119345","DOIUrl":"10.1016/j.epsl.2025.119345","url":null,"abstract":"<div><div>Secular trends in Precambrian calcium carbonate (CaCO₃) sediments that nucleated within the water column or precipitated directly on the seafloor reflect evolving chemical controls on their formation. Previous work has hypothesized that kinetic inhibitor species like ferrous iron (Fe²⁺) significantly raised the free energy barrier to CaCO₃ nucleation and drove alternative mineralization pathways. However, direct evidence for Fe²⁺-inhibition on CaCO₃ precipitation in anoxic seawater is limited. Here we present experimental results on the nucleation of carbonate minerals in simulated anoxic Archean-Paleoproterozoic seawater across a range of ferrous iron concentrations ([Fe²⁺] = 0.05 to 5.0 mmol/kg) and calcite saturation states. With increasing [Fe²⁺] the rate of CaCO₃ precipitation decreased, aragonite increased in abundance over calcite, and calcite crystallites exhibited marked morphological modification. We observed no concentration of ferrous iron at which calcite nucleation is fully suppressed, but at [Fe²⁺] &gt; 1 mmol/kg noted aggregates of variably Ca-rich, Fe(II)-bearing carbonate which may have crystallized from an amorphous Ca-Fe carbonate precursor. Our results suggest that it is unlikely that dissolved iron was present in high enough concentrations to independently control secular trends in Precambrian carbonate sedimentation, but that Fe²⁺-inhibition contributed to maintaining supersaturation with respect to calcite. Furthermore, our results imply that the nucleation of ferroan calcite and/or amorphous Ca-Fe carbonate from supersaturated ferruginous solutions served as an additional and potentially significant sink for iron from the Precambrian oceans.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"660 ","pages":"Article 119345"},"PeriodicalIF":4.8,"publicationDate":"2025-04-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143825920","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A refined isotopic composition of cometary xenon and implications for the accretion of comets and carbonaceous chondrites on Earth","authors":"William S. Cassata","doi":"10.1016/j.epsl.2025.119307","DOIUrl":"10.1016/j.epsl.2025.119307","url":null,"abstract":"<div><div>The origins of Earth's volatiles, including water, remain uncertain. Noble gases can be used to constrain volatile sources as they exhibit significant chemical and isotopic variations amongst Solar System materials that Earth may have accreted. Here, I refine the isotopic composition of cometary xenon (Xe) measured during the Rosetta mission by optimizing its fit to isotopically similar presolar grains in meteorites. Using this composition, I show that Earth's atmosphere can be explained as a mixture of 83.6 ± 3.2% meteoritic, 15.3 ± 2.8% cometary, and 1.1 ± 0.7% fission Xe (1σ; percentages are with respect to ¹³²Xe). This same approach applied to Kr indicates Earth's atmosphere is 72.1 ± 9.5% meteoritic and 27.9 ± 9.5% cometary Kr (1σ; percentages are with respect to ⁸⁴Kr). Carbonaceous chondrites are likely the predominant source of meteoritic Xe. A carbonaceous chondrite accretion mass of 1.8– 5.2 wt.-% of Earth at the 95% confidence interval explains the relative abundances of meteoritic and fission Xe in Earth's atmosphere. Such accretion may have delivered up to 6 – 18 oceans of water to Earth. Conversely, a cometary ice accretion mass of less than 5 × 10^–5 wt.-% of Earth explains the relative abundance of cometary Xe. This would have delivered less than 0.2% of Earth's water. The data further imply a more linear temporal variation in the mass dependent fractionation of atmospheric Xe throughout the first two billion years of Earth history than previously thought.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"660 ","pages":"Article 119307"},"PeriodicalIF":4.8,"publicationDate":"2025-04-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143825919","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Removal of dissolved arsenic from deep seawater around hydrothermal vents and seamounts","authors":"Yuanchen Li ,&nbsp;Guangyong Bo ,&nbsp;Yihua Cai ,&nbsp;Kan Zhang ,&nbsp;Kuanbo Zhou ,&nbsp;Pingping Zhang ,&nbsp;Chenjing Yang ,&nbsp;Tianyu Chen ,&nbsp;Minhan Dai ,&nbsp;Jian Ma ,&nbsp;Zhimian Cao","doi":"10.1016/j.epsl.2025.119351","DOIUrl":"10.1016/j.epsl.2025.119351","url":null,"abstract":"<div><div>Oceanic cycling of arsenic (As) is closely linked to that of nutrient and trace metal elements such as phosphorus (P) and iron (Fe), primarily due to similar particle-reactivity of As and P and their association with particulate carriers including Fe (oxyhydr)oxides. However, this particle scavenging effect is rarely reflected in seawater depth profiles of total dissolved inorganic As (DAs), which typically resemble those of nutrients, generally showing increasing concentrations with depth. Departing from conventional views, we observed distinct decreases in DAs concentration in deep waters around independent deep-sea systems in the subtropical western North Pacific: hydrothermal vents, seamounts, and island sediments. DAs removal corresponds to elevated dissolved and total dissolvable particulate Fe concentrations, indicating a major control of particle adsorption on As behavior in specific deep-ocean regions. Particle scavenging effect varied among the three deep-sea regions, mainly ascribed to varying particulate elemental compositions, and influence of temperature, pH, and dissolved oxygen. Our findings highlight a previously overlooked sink term for DAs removal from seawater by particles of various deep-sea origins. Newly estimated output fluxes around hydrothermal or seamount systems are comparable to the individual input flux from rivers, atmosphere, and hydrothermal vents, thus helping to balance the global oceanic As budget.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"660 ","pages":"Article 119351"},"PeriodicalIF":4.8,"publicationDate":"2025-04-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143828973","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The contribution of mechanoradical reactions to crustal hydrogen generation","authors":"Nicolas Lefeuvre ,&nbsp;Laurent Truche ,&nbsp;Frédéric-Victor Donzé ,&nbsp;Johan Vandenborre ,&nbsp;Eric C. Gaucher ,&nbsp;Valérie Magnin","doi":"10.1016/j.epsl.2025.119363","DOIUrl":"10.1016/j.epsl.2025.119363","url":null,"abstract":"<div><div>Hydrogen (H₂) generation within the Earth's crust contributes significantly to abiotic organic synthesis and the sustenance of deep microbial ecosystems. While natural H₂ is recognized as a potential primary energy resource, current exploration models focus solely on two sources, serpentinization and water radiolysis, leaving other H₂-generating processes largely unexplored. This study investigates mechanoradical reactions specifically, H₂ production resulting from mineral grinding in the presence of water, a process analogous to rock abrasion along fault planes during earthquakes. We performed laboratory experiments simulating these conditions by grinding quartz under controlled conditions of fluid pH, ionic strength, water/rock (W/R) ratio, and grinding energy. Our results show that H₂ production is significantly affected by these parameters. Notably, grinding in acidic environments (6&lt; pH &lt; 4) tripled H₂ production compared to alkaline conditions (pH &gt;8). Increasing the W/R ratio from 0.1 to 1 resulted in an 18-fold enhancement of H₂ production. Additionally, a linear relationship was observed between H₂ production and the grinding energy applied. Extrapolating our findings to natural fault movements, we estimate that mechanoradical reactions during earthquakes of magnitude greater than 4 generate approximately 1.45 <span><math><mo>×</mo></math></span> 10¹³ mol yr^-1 of H₂. Although this production rate involved significant incertainties related to the model assumptions and may not be directly compared to serpentinization and radiolysis - since these H₂-producing processes operate on different time and space scales - our study underscores the importance of including mechanoradical processes in models of crustal H₂ fluxes. Recognizing these reactions expands our understanding of subsurface H₂ generation and its contributions to geochemical and microbial processes in the Earth's crust.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"660 ","pages":"Article 119363"},"PeriodicalIF":4.8,"publicationDate":"2025-04-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143823790","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Seismic azimuthal anisotropy of New Zealand revealed by adjoint-state traveltime tomography","authors":"Shucheng Wu ,&nbsp;Jing Chen ,&nbsp;Ping Tong","doi":"10.1016/j.epsl.2025.119362","DOIUrl":"10.1016/j.epsl.2025.119362","url":null,"abstract":"<div><div>The omission of seismic anisotropy in current reference models covering the entire New Zealand has been an obstacle to achieving a comprehensive understanding of deformation and dynamics along the complex Pacific-Australian plate boundary segment. Here we present a 3D azimuthally anisotropic model that encompasses both the North and South Islands of New Zealand to a depth of 40 km, using over 1 million local P-wave arrival times and a newly developed adjoint-state traveltime tomography technique. This model is built upon the New Zealand-wide 3D isotropic velocity model, serving as an essential and incremental update to the existing model. Our new model highlights significant variations in anisotropy across the plate boundary region, indicating distinct deformation states between tectonic blocks. In the North Island, pronounced along-strike changes in anisotropy are evident beneath the Hikurangi forearc, which could be attributed to variations in stress regime associated with the oblique plate convergence and changes in interseismic coupling of the subduction megathrust. The oblique plate motion further induces pure shear deformation in the middle to lower crust of the southern backarc, resulting in strong anisotropy with fast axes perpendicular to the principal axes of maximum horizontal compression. In contrast, seismic anisotropy in the central South Island primarily stems from the preferential alignment of minerals, notably within the Haast schist in the Otago block. However, anisotropy in the middle to lower crust of the northern South Island may represent inherited structures that originated during past southward subductions along the Gondwana margins at ∼100 Ma. Our new model offers valuable insights into the intricate geological processes occurring within the plate boundary region.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"660 ","pages":"Article 119362"},"PeriodicalIF":4.8,"publicationDate":"2025-04-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143823794","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}